Refactor to use .belongs_to methods

The view code shouldn’t need to know the internals of a service’s data
structure; the idea of having a service model is to abstract this kind
of thing.

app/main/views/choose_account.py

@@ -31,11 +31,11 @@ def show_accounts_or_dashboard():
         return redirect(url_for('.index'))
 
     service_id = session.get('service_id')
-    if service_id and (service_id in current_user.service_ids or current_user.platform_admin):
+    if service_id and (current_user.belongs_to_service(service_id) or current_user.platform_admin):
         return redirect(url_for('.service_dashboard', service_id=service_id))
 
     organisation_id = session.get('organisation_id')
-    if organisation_id and (organisation_id in current_user.organisation_ids or current_user.platform_admin):
+    if organisation_id and (current_user.belongs_to_organisation(organisation_id) or current_user.platform_admin):
         return redirect(url_for('.organisation_dashboard', org_id=organisation_id))
 
     if len(current_user.service_ids) == 1 and not current_user.organisation_ids:

app/models/user.py

@@ -228,6 +228,9 @@ class User(JSONModel, UserMixin):
         if not self.belongs_to_service(service_id):
             abort(403)
 
+    def belongs_to_organisation(self, organisation_id):
+        return str(organisation_id) in self.organisation_ids
+
     @property
     def locked(self):
         return self.failed_login_count >= self.max_failed_login_count